The invention relates to the field of maritime hydraulics and more particularly it relates to a refinement of the device for attenuating sea swell in the form of a so-called “camel's back” described in European Patent EP 0 381 572 B1.
Devices for attenuating sea swell are well known. They enable any site, for example maritime structures, coastal or offshore installations or even ports, to be protected from the energy of the incident waves breaking against these sites.
The most popular devices rely on rock-filled slopes or concrete structures lying on the marine substrate, or a combination of the two, which rising from the sea-bed thus form a vertical obstacle for the incident waves.
Now, sea swell being an undulatory phenomenon, it appeared more advantageous to exploit this phenomenon in order to obtain a swell wave transmitted to the site to be protected, having an appreciably reduced amplitude compared to the wave from incident sea swell. It is the object of European Patent No 0 282 479 B1, published in the name of the Monaco Government and disclosing a sea swell attenuator exploiting a particularly novel principal and known since under the name of “fixed wall of water”. This device comprises a horizontal plate held slightly immersed in the incident sea swell, the upstream and downstream edges of which are raised to a positive dimension above the free surface of the water so that the incident sea swell cannot propagate freely above the plate. For suitable dimensioning of the plate, relative to the incident sea swells, the mass of water imprisoned beneath the plate can have only horizontal displacements and behaves overall like a homogeneous inert obstacle with respect to the incident sea swell, which swell is reflected on this “fixed wall of water”.
This device, which is totally satisfactory for sea swells of short duration (less than 5 seconds), however for sea swells of longer duration generates a lapping effect, which acts unfavourably on the amplitude of the swell wave transmitted to the site to be protected. This is why, in European Patent No 0 381 572 B1 mentioned above, also published in the name of the Monaco Government, a refinement of the sea swell attenuation device which makes it possible to avoid this lapping effect, has been proposed. A preferred example of a refined device of this kind is illustrated in FIGS. 6 to 8 of this European Patent, which shows a horizontal plate having a symmetrical profile in the form of a so-called “camel's back”. This refined device, of which an embodiment is today operational in the port of Condamine in the Principality of Monaco, is totally satisfactory for a very wide range of swell durations. However it was apparent that, for sea swells of long duration (from 6 to 10 seconds), the horizontal and vertical hydrodynamic efforts and the moments of inversion acting on the device were significant. Their reduction would therefore be likely to minimize the dimensioning both of the structures of the attenuator as well as of its supports or connections.